Ambisonics is an effective technique to encode and reconstruct sound fields. This technique is based on the orthogonal decomposition of a sound field in the spherical coordinates in the 3D space or cylindrical decomposition in the 2D space. In the decoding process, the ambisonic signals are decoded to produce speaker signals. The higher the order of the ambisonics, the finer reconstruction of the sound fields achieved.
Moreover, the complexity of the sound field plays a key role in the quality of the reconstructed sound field for a given ambisonics order. A less complex sound field might be well described by low-order ambisonics whereas a more complex sound field requires Higher-Order Ambisonics (HOA) to be reconstructed with high quality. A complex sound field contains many simultaneous active sources (either localized or distributed sources). If at any time instance (or in a frequency band) there are few active sources, lower order ambisonics would be able to describe and encode the sound field.